It is always interesting to find out how the public discovers change in their local scenery and their resulting attitudes. The perception with Biology is incredible, and it usually takes an unprecedented activity to open eyes.

The Fall of 2008 in southern Arizona has had one of those phenomena occur right in front of everyone. Mesquites of course are a dominant tree here, so when something causes change in dramatic fashion, people see it. Walk into your yards and look at your mesquites and the chances are you’ll see a dead twig or two amongst the foliage, or more. This has been occurring every year, but in 2008, the population boom of a small long-horned beetle Oncideres rhodosticta, called the mesquite twig girdler has suddenly made everyone notice. Typically the beetle isn’t seen working on the tree, but if you go to a gas station or market where bright lights abound at night, you will have encountered these beetles by the hundreds this year. They fly, they land on you, their claws catch in your clothing, and they may even grab hold with their jaws, not to be mean and bite, but simply to maintain a purchase on the substrate (You). Don’t panic, for they won’t eat you, vector a disease or make you sick. In fact, take the time to look and you will be amazed by the colors and designs exhibited on the exoskeleton. Yes, bugs are neat and interesting if one dispels the prejudice and understands them as wildlife.

What does this little beetle do, and why? The adults emerge in August as the monsoon season is winding down, mate and then select a mesquite, or sometimes an acacia, as home base. The female then proceeds to chew a ring around a twig, stopping the flow of sap and eventually causing that part of the twig to die. She has prepared a nursery for her offsping, allowing her to lay eggs in the dead part, knowing her eggs have a good chance to survive. If one looks along the dead part, you can see white, lens-shaped marks that are the egg-laying sites. Those eggs will hatch in a week or two and begin feeding and growing under the bark of the twig. By the next summer the larvae will pupate and prepare to emerge in late August for the next cyclical event.

Now for perception. As an entomologist at the University of Arizona, I am bombarded by questions about insects. The first question has been, what is killing my mesquite trees, because folks see a dead twig tip or more, and immediately decide the tree is dying? The reality is, those beetles have simply pruned the mesquites, which will result in more twig growth in the future. Now this pruning may not agree with your ways, but Nature does have a method. Not death except for twig tips, but rather a healthy, vibrant tree. For the obsessively neat of course this is traumatizing because the trees are not nice and green but sprinkled with brown flags. Oh well, trim the dead branches and one is back to perfection. And of course, people want to do something to prevent such a devastating course of events, but truth is, there is nothing to do.

As I said, perceptions occur in many ways, and the best view passed along to me was from a person who was looking at the mesquites with the sun shining through the branches, and felt the trees were golden. On closer examination, he saw globs of sap had dripped from the girdle and the sunrays were reverberating through and from these balls of sap, producing an exquisite new image to the mesquites. Yes, people can see ugly or beauty, but to me beauty is life, excitement and joy, which these beetles create every year, just more this year.